Biogeography of mediterranean hotspot biodiversity: re-evaluating the'tertiary relict'hypothesis of macaronesian laurel forests

The Macaronesian laurel forests (MLF) are dominated by trees with a laurophyll habit com parable to evergreen humid forests which were scattered across Europe and the Mediterra nean in the Paleogene and Neogene. Therefore, MLF are traditionally regarded as an old, 'Tertiary relict' vegetation type. Here we address the question if key taxa of the MLF are relictual. We evaluated the relict hypothesis consulting fossil data and analyses based on molecular phylogenies of 18 representative species. For molecular dating we used the pro gram BEAST, for ancestral trait reconstructions BayesTraits and Lagrange to infer ancestral areas. Our molecular dating showed that the origins of four species date back to the Upper Miocene while 14 originated in the Plio-Pleistocene. This coincides with the decline of fossil laurophyllous elements in Europe since the middle Miocene. Ancestral trait and area recon structions indicate that MLF evolved partly from pre-adapted taxa from the Mediterranean, Macaronesia and the tropics. According to the fossil record laurophyllous taxa existed in Macaronesia since the Plio- and Pleistocene. MLF are composed of species with a hetero geneous origin. The taxa dated to the Pleistocene are likely not 'Tertiary relicts'. Some spe cies may be interpreted as relictual. In this case, the establishment of most species in the Plio-Pleistocene suggests that there was a massive species turnover before this time. Alter natively, MLF were largely newly assembled through global recruitment rather than surviv ing as relicts of a once more widespread vegetation. This process may have possibly been triggered by the intensification of the trade winds at the end of the Pliocene as indicated by proxy data.

Keywords

Biogeography Biodiversity Macaronesian Laurel forests Laurel forests Mediterranean biodiversity Tertiary relict . Faculdade de Ciências da Vida

URI

http://hdl.handle.net/10400.13/4195

Citation

Kondraskov, P., Schütz, N., Schüßler, C., Sequeira, M. M., Guerra, A. S., Caujapé-Castells, J., ... & Thiv, M. (2015). Biogeography of mediterranean hotspot biodiversity: re-evaluating the'tertiary relict'hypothesis of macaronesian laurel forests. PloS one, 10(7), e0132091. DOI:10.1371/journal.pone.0132091